What is this in my lens?

Alright so i am having a tough time figuring out what this is on my 12-24mm dx nikon that i bought off somebody not too long ago and i was hoping somebody could help who has seen similar or is experienced.It's a long shot since the images are not amazing and that usually it's tough to tell without a magnifier or taking apart the lens itself.It can only be seen with a torch and is basically invisible with natural light or barely barely visible if you dont really know what to look at. It can be seen on the other side of the barrel though i couldn't get a decent picture of that because im using the torch on my camera phone.I am hoping it isn't fungus and that i didn't get ripped off.Thanks for any help !